Jordan Christian, a postdoctoral researcher, is the lead author of the study, “Global projections of flash drought show increased risk in a warming climate,” published today in Nature Communications Earth and Environment.

“In this study, projected changes in flash drought frequency and cropland risk from flash drought are quantified using global climate model simulations,” Christian said. “We find that flash drought occurrence is expected to increase globally among all scenarios, with the sharpest increases seen in scenarios with higher radiative forcing and greater fossil fuel usage.”

Radiative forcing describes the imbalance of radiation where more radiation enters Earth’s atmosphere than leaves it. Like burning fossil fuels, these activities are among the most significant contributors to climate warming. The changing climate is expected to increase severe weather events from storms, flash flooding, flash droughts and more.

“Flash drought risk over cropland is expected to increase globally, with the largest increases projected across North America and Europe,” Christian said.

“CMIP6 models projected a 1.5 times increase in the annual risk of flash droughts over croplands across North America by 2100, from the 2015 baseline of a 32% yearly risk in 2015 to 49% in 2100, while Europe is expected to have the largest increase in the most extreme emissions scenario (32% to 53%), a 1.7 times increase in annual risk,” he said.

Jeffrey Basara, an associate professor in the School of Meteorology in the College of Atmospheric and Geographic Sciences and the School of Civil Engineering and Environmental Sciences in the Gallogly College of Engineering, is Christian’s faculty advisor and study co-author. Basara is the executive associate director of the hydrology and water security program and leads OU’s Climate, Hydrology, Ecosystems and Weather research group. The researchers have been investigating ways to improve flash drought identification and prediction since 2017, with multiple papers published in the Journal of Hydrometeorology, Environmental Research Letters and Nature Communications.

“This study continues to emphasize that agricultural producers, both domestic and abroad, will face increasing risks associated with water availability due to the rapid development of drought. As a result, socioeconomic pressures associated with food production, including higher prices and social unrest, will also increase when crop losses occur due to flash drought,” Basara said.

But how? And why? A new study from researchers at Western’s Advanced Facility for Avian Research (AFAR), home to the world’s first hypobaric climatic wind tunnel for bird flight, explores a brain region called cluster N that migratory birds use to perceive Earth’s magnetic field. The team discovered the region is activated very flexibly, meaning these birds have an ability to process, or ignore, geomagnetic information, just as you may attend to music when you are interested or tune it out when you are not.

More specifically, the research team led by psychology PhD candidate Madeleine Brodbeck and AFAR co-director Scott MacDougall-Shackleton studied white-throated sparrows and found they were able to activate cluster N at night when they were motivated to migrate (to avoid prey and fly during cooler periods) and make it go dormant when they were resting at a stopover site

This is the first demonstration of this brain region functioning in a North American bird species, as all prior research in this area was completed in Europe.

“This brain region is super important for activating the geomagnetic compass, especially for songbirds when they migrate at night,” said Brodbeck. “Almost all previous work on this specific brain function was done at one lab in Europe, so it was great to replicate it in a North American bird like the white-throated sparrow.”

Earth’s magnetic field, likely first investigated and identified by German mathematician Carl Friedrich Gauss in the 1830s, has long fascinated physicists, aerospace engineers and even science fiction writers like Frank Herbert and Stephen King. Brodbeck, a bird psychologist, is equally intrigued.

“Magnetic fields are really fun to think about because they’re invisible to humans. We can’t see them or sense them, but most animals perceive them in some way,” said Brodbeck. “For birds, using Earth’s magnetic field to know if they’re going towards a pole or towards the equator is obviously really helpful for orientation and migration. It’s incredible that they can activate their brain in this way, and we can’t.”

Understanding the physical mechanisms of how animals make their way around in the world is a fundamentally important question for researchers, says MacDougall-Shackleton, a psychology professor and cognitive neuroscientist.

“If we want to understand bird migration or how other animals move from one place to another, we need to know how they do it. And more importantly, we need to know what we’re doing, as humans, that might influence them,” said MacDougall-Shackleton.

The findings were published in the journal, European Journal of Neuroscience.

“Birds don’t just use their magnetic compass. We know they pay attention to the Sun and the stars as cues too. And we also know that things like lights at night, or windows in buildings, and all these things that we put in the world disrupt their migrations,” said MacDougall-Shackleton. “This type of basic research informs us and lets us know the full suite of ways that animals perceive the world when they’re migrating and what we as humans need to do to minimize our impact.”

This new research, “Low temperature absolute internal quantum efficiency of InGaN-based light-emitting diodes,” was recently published in Applied Physics Letters.

As ECE associate professor Can Bayram puts it, LEDs are the ultimate lighting source. Since their invention, they have become increasingly popular due to their energy efficiency and cost-effectiveness.

An LED is a semiconductor that emits light when current flows through the device. It generates photons through the recombination of electrons and holes (carriers), releasing energy in the form of photons. The color of the light emitted corresponds to the energy of the photon.

InGaN-based blue LEDs enable bright and energy-saving white lighting. The transition to solid-state lighting sources has significantly reduced energy needs and greenhouse gas emissions, but continual efficiency improvements are necessary to hit energy savings goals in the long term. The U.S. Department of Energy’s 2035 roadmap calls for blue LED efficiency to increase from 70% to 90% and furthering energy savings by 450 terawatt hours (TWh) and CO₂ emission savings by 150 million metric tons.

Bayram says, “The question is, how can we push this ultimate lighting source further? The answer is by understanding its absolute efficiency, not relative efficiency.” Relative efficiency benchmarks a device with itself, while absolute efficiency allows for comparison across different devices by measuring the efficiency on a commonly shared scale.

IQE is defined as the ratio of the generated photons to the injected electrons in the active region of the semiconductor and is an important metric to quantify the performance of LEDs. The most widely used method to quantify IQE is by temperature-dependent photoluminescence. In such analyses, it has been assumed that at low temperatures (4, 10, or even 77 Kelvin), there is 100% radiative recombination- meaning producing a photon. At room temperature, because of non-radiative mechanisms- which emit excess energy as heat, rather than photons- the efficiency is significantly lower. The ratio of the two photoluminescence intensities gives a relative efficiency of the LED.

The original assumption has been that at low temperatures, there are no non-radiative recombination- all the loss mechanisms are “frozen.” Bayram and graduate student Yu-Chieh Chiu assert, however, that this assumption may be wrong because non-radiative effects might not in fact be completely frozen out at low temperatures.

In their paper, Bayram and Chiu demonstrate a different method for revealing low temperature absolute IQE of InGaN-based LEDs. Using a “channel-based” recombination model, they report surprising results: the absolute IQE of the LED on traditional sapphire and silicon substrates is 27.5% and 71.1%, respectively- drastically lower than the standard assumption.

To explain these unexpected results, Chiu says that the channel-based recombination model is one of the ways to think about what happens inside the active layer of the LED and how recombination in one channel affects another channel. A channel is a pathway that a carrier may take to recombine radiatively or nonradiatively.

“To determine the efficiency of the blue LED, usually only the blue emission is considered,” Chiu says. “But that ignores the effects of everything else happening inside the device, specifically the non-radiative and defect luminescence channels. Our approach is to get a more holistic view of the device and determine, if there is recombination in the blue channel, how is that affected by the second and third channel(s)?”

As research on the LED continues to advance, it is important to know an absolute efficiency rather than a relative efficiency. Bayram stresses that “the absolute efficiency is very important to the field so that everyone can build on each other’s knowledge rather than each group improving their own efficiency. We need absolute measurements, not just relative measurements.”

To meet the efficiency standards laid out by the DOE, it will be increasingly important to properly quantify the efficiency of LEDs. Even a 1% increase in efficiency will correspond to tons of carbon dioxide savings annually. Chiu says, “By understanding the absolute efficiency, instead of the relative efficiency, that will give us a more accurate picture and allow us to improve devices further by being able to compare them to each other.”

Traces of an unusual process

When dielectrons are formed by excitation with ultraviolet light in tiny ammonia droplets containing a sodium atom, they leave traces in an unusual process that scientists have now been able to observe for the first time. In this process, one of the two electrons migrates to the neighbouring solvent molecules, while at the same time the other electron is ejected. “The surprising thing about this is that similar processes have previously been observed mainly at much higher excitation energies,” says Hartweg. The team focused on this second electron because there could be interesting applications for it. On the one hand, the ejected electron is produced with very low kinetic energy, so it moves very slowly. On the other hand, this energy can be controlled by the irradiated UV light, which starts the whole process. Solvated dielectrons could thus serve as a good source of low-energy electrons.

Generated specifically with variable energy

Such slow electrons can set a wide variety of chemical processes in motion. For example, they play a role in the cascade of processes that lead to radiation damage in biological tissue. They are also important in synthetic chemistry, where they serve as effective reducing agents. By being able to selectively generate slow electrons with variable energy, the mechanisms of such chemical processes can be studied in more detail in the future. In addition, the energy made available to the electrons in a controlled manner might also be used to increase the effectiveness of reduction reactions. “These are interesting prospects for possible applications in the future,” says Hartweg. “Our work provides the basis for this and helps to understand these exotic and still enigmatic solvated dielectrons a little better.”

Traditional synthetic biology approaches for cell-based therapies, such as ones that destroy cancer cells or encourage tissue regeneration after injury, rely on the expression or suppression of proteins that produce a desired action within a cell. This approach can take time (for proteins to be expressed and degrade) and cost cellular energy in the process. A team of Penn State College of Medicine and Huck Institutes of the Life Sciences researchers are taking a different approach.

“We’re engineering proteins that directly produce a desired action,” said Nikolay Dokholyan, G. Thomas Passananti Professor and vice chair for research in the Department of Pharmacology. “Our protein-based devices or nano-computing agents respond directly to stimuli (inputs) and then produce a desired action (outputs).”

In a study published in Science Advances today (May 26) Dokholyan and bioinformatics and genomics doctoral student Jiaxing Chen describe their approach to creating their nano-computing agent. They engineered a target protein by integrating two sensor domains, or areas that respond to stimuli. In this case, the target protein responds to light and a drug called rapamycin by adjusting its orientation, or position in space.

To test their design, the team introduced their engineered protein into live cells in culture. By exposing the cultured cells to the stimuli, they used equipment to measure changes in cellular orientation after cells were exposed to the sensor domains’ stimuli.

Previously, their nano-computing agent required two inputs to produce one output. Now, Chen says there are two possible outputs and the output depends on which order the inputs are received. If rapamycin is detected first, followed by light, the cell will adopt one angle of cell orientation, but if the stimuli are received in a reverse order, then the cell adopts a different orientation angle. Chen says this experimental proof-of-concept opens the door for the development of more complex nano-computing agents.

“Theoretically, the more inputs you embed into a nano-computing agent, the more potential outcomes that could result from different combinations,” Chen said. “Potential inputs could include physical or chemical stimuli and outputs could include changes in cellular behaviors, such as cell direction, migration, modifying gene expression and immune cell cytotoxicity against cancer cells.”

The team plans to further develop their nano-computing agents and experiment with different applications of the technology. Dokholyan, a researcher with Penn State Cancer Institute and Penn State Neuroscience Institute, said their concept could someday form the basis of the next-generation cell-based therapies for various diseases, such as autoimmune diseases, viral infections, diabetes, nerve injury and cancer.

Yashavantha Vishweshwaraiah, Richard Mailman and Erdem Tabdanov of Penn State College of Medicine also contributed to this research. The authors declare no conflicts of interest.

This work was funded by the National Institutes of Health (grant 1R35GM134864) and the Passan Foundation.